Means for thermally generating electricity



Sept. 24, 1935. E. UNDERWOOD MEANS FOR THERMALLY GENERATING ELECTRICITY Filed Dec. 22, 1932 3 Sheets-Sheet 1 d 0 M H wr N mm m w fin. /A a N M w L. ow

Sept. 24, 1935; E. UNDERWOOD 10 MEANS FbR THERMALLY GENERATING ELECTRICITY I fgya. under-wood [/VVf/VTOA Sept. 24, 1935. E, UNDERWQQD 2,015,610

MEANS FOR THERMALLY GENERATING ELECTRICITY Filed Dec. 22, 1932 3 Sheets-Sheet 3 [gar an derw ood z/v v m-0R ATTORNEYJ Patented Sept. 24,

PATENT: OFFICE MEANS on 'rminM'ALLY GENERATING ELECTRICITY 2 Edgar Underwood, Gary, Ind. Application December 22, 1932, Serial No. 648,513 2 Claims. (Cl. 136-4) My invention relates to improvements in means of thermally generating electricity, andit consists in the combinations, constructiohaand arrangements herein described and claimed. An object of my invention is to provide an efficient method and means of thermally generating electricity.

Another object is to provide means whereby heat energy may be rapidly transferred from the cold junctions of a thermopile to its hot junctions. A further object is to provide a fan or air pump meanswhereby cool air may be rapidly passed over the cold junctions and the temperature of a portion of this air then raised by compression and 15, the remainder of the alrre-heated by conduction for passing into the combustion'chamber in which the hot junctions of my thermopile are heated.

A further object of my invention is the efficient employment of extremely shortthermo- 20 couple elements to the end that the electrical resistance of the thermo-couple elements may be substantially decreased.

A further object is to provide means whereby the thermo-couple elements may be supported 25 'even when embedded in a comparatively thinand flexible insulating roof or wall.

A further object is to provide means whereby the hot junctions of the thermo-couple may be protected from direct contact with the heated 30 particles of combustion in the furnace chamber.

A further object is the provision of a thin flexible insulating wall permitting the safe em-' ployment of short thermo-couple elements.

\ A further object of my invention is to provide 35, means whereby the voltage of a thermoelectric generator may be regulated by controlling the fuel input. 1 I

A further object is the provision of meanswhereby the thermo-couple elements and the in- ,40 sulating wall may be securely supported.

A further object is the provision of means whereby the heat which is transferred by conduction from the hot junctions to the cold junctions of a thermopile may be rapidly removed 45 from the cold junctions.

A further object is the pre-heating of the fuel by heat energy derived from the heated products of combustion after the products of combustion have passed from the combustion chamber of the 50 furnace.

Other objects and advantages will appear in the following.v specification, and the novel features of the invention will be particularly pointed out in the appended claims.

5% My invention is illustrated in t e accompanyin:i drawings, forming part of this application, in w ch v Figure 1 is a. partly broken away top plan view of a preferred form of a thermoelectric generating system embodying my invention, 5

Figure 2 is a section taken along the line 22 of Figure 1, certain portionsbeing shown in section l, p

Figure 3 is a section taken along the line 3-8 of Figure 2. lit

Figure 4.. is a section taken substantially along the lined-4 of Figure 1 Figure 5 is a section taken along the line 5 -5 of Figure 4, Figure 6 is a section taken along the line 8-6 of Figure 4, 1 Figure '7 is a front elevational view of the construction shown in Figure 1,

Figure 8 is a partly sectional partly diagrammatic view of a fuel control means whereby the voltage of my thermoelectric system be regulated, Figure 9 is a fragmentary vertical sectional view of a modified form of my invention, Figure 10 is abroken vertical section through the lower end of one of the thermocouples, and

Figure 1 l is a sectional view taken on line l l! I of, Figure 10.

in carrying out my invention I make use of a firebox I which is preferably mounted above a fireproof floor Z on a rigid supporting member or base plate 3, having a. central opening d and being supported on any suitable legs 5. The walls 6 and. the bottom I of the firebox are preferably made of heat resisting material such as, for instance, 3.5

asbestos composition bricks. 7 Above the opening 4 of the plate 3, a rigid frame 8 is provided for supporting a burner means 9 and a primer means It. The frame 8 may, if desired, be bolted to the bottom of the base I of 40 the firebox. The function of the primer I B is to initially heat and vaporize the fuel in the burner 9. I

The top of the firebox comprises a heat insulating and heat resisting board i I, which is preferably of asbestos composition, and isarranged or adapted to provide a seal whereby the products of combustion .are prevented from passing from the roof of the firebox.

A plurality of hereinafter to be described thermo-couple elements are imbedded in and extend through this insulating board. The upper portion terior of my generating system.

The conduit I3 extendsfroman opening 4 (where air is received from the upper portion of my system) down to the opening 4 in the base plate 3, which supports the firebox. v

The lower portion of the conduit I 3 is secured to the plate 3 in such a manner that no air may enter the firebox through the opening 4 except the air which is passed downwardly through the conduit I3.

The burner 9 and the primer ID are suppliedwith liquid fuel from a tank [5, see Figure 8, by way of a main pipe 16, see Figure 4, to which the burner fuel pipe I! and the primer fuel pipe l8 are operatively connected. Each of the pipes l1 and I8 pass through the wall of a conduit l3 in an air tight manner. The primer pipe is directly connected to the primer substantially as shown. The fuel pipe passes to the rear and then upwardly through the conduit l3 and then passes into the exhaust conduit l2, where it is coiled as is indicated at l9, so that the fuel may be thoroughly vaporized before it passes out of the inner end of the conduit l2, and is operatively connected to the burner 9. Each of these pipes may be provided with any suitable valve means such as for instance hand valves 20 and 2|.

Now'referring to Figures 1 to 4 inclusive, it will be seen that a plurality of parallel pipes 22 are supported above the firebox by brackets23, which are mounted on top of the firebox at the front and the rear of my electric generator substantially as shown in Figure 1. These brackets may be of any suitable construction adapted to support the pipes and at the same time permit a substantially unobstructed flow of air from the front to the rear of the generator. Each of these pipes may be insulated in any suitable manner, such as for instance, by an insulating sleeve 24. This insulating sleeve may be made of asbestos or any other suitable construction adapted to withstand a certain amount of heat, and atthe same time provide an electrical insulation between its pipe and the strap 7 and thermocouple means now to be described.

Now referring particularly to Figure 2, it willbe seen that the pipes 22 support a plurality of'thermocouples by means of straps 25. These straps may be made of a steel alloy and for the purpose of illustration are shown as each consisting of two strips which are bolted together at the top of the pipes, as is indicated at 26, and extend downwardly to support the thermocouple elements 21.

- These strips are secured to the opposite sides of a thermocouple unit by means of a brad or bolt 28 which passes entirely through the cold Junction 29 of the thermocouple unit and each of the strips, and by welding.

These thermocouple elements are, of course, of metal construction. While these may be made of any metals having an electrical potential difference when heated, in the present instance I have used a nickel chrome alloy strip 30 in comb1nation with a copper nickel alloy stripfl. I have found this combination of alloys to be suitable for 'the purpose intended, and to have a fairly low resistance when heated.

The copper nickel alloy when heated acts as a positive or negatively charged element, and the nickel-chrome alloy acts as a negative OPPOSI- tively charged element.

, other of the terminal strips 'rality of openings 43 through and the hot junction end being parallel and offset with respect to each other, and these two ends being connected together by an inclined portion which is approximately one third the length of 'the entire length of these elements.

The hot junction may be joined together in the same manner as the cold junction with the exception, of course, that the straps are not connected to the hot junction. The hot junction is shielded from direct contact-with the heated products of 10 combustion by a metal casing'80 which is preferably cup-shaped and is fixedly secured to the hot junction inany suitable manner such as, for instance, rivets or bolts 28'. or by welding.- The preferred construction of the casing is illus- 15 trated in Figures 10 and 11. The couple elements 30 and 3! preferably are welded together and ,may be provided also with a rivet. if desired.

Welded to opposite sides of the connected ends of the elements 30 and 3| are plates 80a and 80b 20 which extend beyond the vertical sides and bottom edges of the elements to form a channel in which weld material 800 is deposited to form with the said plates of the inclosing cup or 'casing 80. The welding of the elements 30 and 3| together and the forming of the casing 80 as described, not only protects the couple elements. but reduces the resistance of the couple and thus increases its efficiencv. The casing 80 together with the inclosed ends of the'couple elements constitute heat ab- 30 sorbers.

By referring to Figures 1 and 4 it will be seen that one of the terminal strips 32 is connected to the rear far portion of the thermopile, while the near front end of the thermopile.

The portion of the thermopile construction which extends above the insulating board II is enclosed in the metal casing or cover 36 which in combination with the board II forms an elongated air casing or conduit 31 through which air is 33 is connected to the 35 is that they serve as radiators and conduct the 45 heat rapidly away from the cold junctions and due to their comparatively large surface area transmit this heat rapidly to the airstream passing through the casing.

-The front portion of 'the cover 36'extends beyond and in front of the firebox I, and supports an electrical fan means 39, having a motor 40.

In the rear and opposite portion of the air casing 31 a funnel shaped air exhaust conduit 4| is provided for the purpose of constricting a major 55 portion of the air after it has passed over and has been heated by part of the thermopile construction which extends above the insulating boardfl I This air exhaust is provided with a funnel portion 42, the outer peripheral edge of which is 50 weldedor otherwise connected in a substantially air tight manner to the'inside of the casing 36, see Figure 5, to the end that the air driven through the casing may be forced into the funnel portion 42. This funnel portion 42 is provided with a pluwhich a minor portion of the air stream, after passing by the thermopile, may pass around the outside of the funnel tube 44, for the purpose which will become ap-,

parent as the specification proceeds. The main or 70 major portion of the air stream is forced by the fan 39 into the funnel portion 42 to pass through the-tube 44 and out of the rear end of the easing 36.

This funnel tube is provided with a plurality 7a of metal fins 45 which may pass entirely through the funnel andproject on either side thereof substantially as shown in Figure 5. The outer ends of these fins preferably do not touch the surrounding walls of the air casing 31, as it istheir function to heat the minor portion of the air stream in a manner more fully set forth in the description of the operation of my generating system.

The minor stream, ter passing betweenand being heated by these fins, passes out of the casing 31 through the openiri l4 in the rear bottom portion 31' of the casing, and thereafter passes downwardly through th conduit l3 and discharges into the hollow I terior of the firebox I.

In Figure 8 I have shown an electro-magnetically operated switch and valve construction whereby the voltage generated in my thermoelectric generatlngsystem may be maintained within predetermined limits, and thereby kept substantially constant during the normal operation of my system. This switch and valve construction includes a valve means 45, a solenoid", and an electric switch means 48. Each of the means 46, 41 and 48 may be mounted on any suitable support, such as for instance a switch board 49, and may be operatively connected together, substantially as shown.

The valve means 45 includes a chambered body portion 50 and an exteriorly threaded cup shaped packing ring having a cap 5|. The ,body portion 5|] is provided with a valve chamber 52 having inlet and outlet ports 53 and 55, operatively connected to the fuel supply tank |5 and the main pipe l5, substantially as shown.

The valve chamber 52 is provided with a valve seat 55 which is adapted to receive the valve 55 which is rigidly secured to a rod 51. This rod- 51 passes through the packing ring cup member 5|, and at its upper end is rigidly secured to a reciprocating plunger armature 58; this plunger armature is operated by an electrical energizing coil 41 in such a manner that when the coil is energized the plunge 55 tends to move downwardly, thus closirg/thevalve 56, on the valve seat 55. The plunger armature 58 is connected at its upper end to a vertical rod 59 which in turn is pivotally connected at its upper endto a switch arm 60 which is pivotally mounted at 43' in an opening 44' and is arranged to connect the nected with the rod 55 and the uppermost of the brackets 45' supporting the coil 41.

The terminal 8| and the coil 41 may be electrically connected to the terminal members 32 and 33, substantially as indicated in Figure 8.

From the foregoing description of the various parts of my invention, the operation thereof may be thoroughly understood. when the generator is cold, it will be noticed that the valve 56 is kept in its open position by the tension of the'spring 62 surrounding the rod. 59. The liquid fuel from the tank I5 may, there- I fore, pass into the primer feed pipe l5, and may be admitted to the 'primer by-opening the hand valve 2|. When the liquid fuel in the primer is "ignited itpOf course, heats the burner 5. A sumciently hot fuel may be admitted to. the burner 5.

heated when the burner is in operation, and the exhaust products of combustion pass out of the system through the rectangular exhaust conduit, |2.' In passing through the conduit |2 the heat. oi these products of combustion almost immediately vaporize the liquid fuel in the coil of the pipe H. The hand valve 2| may now be closed, shutting off the fuel from the primer ID. The heating of the-lower or hot junctions of the thermopile generates an electromotive' force proportional to the difference in temperature between the hot junctions and the cold junctions of the thermopile. The terminal strips 32 and 33, therefore, if connected as indicated in Figure 8, pass a current through the conductors 5g, 66, I1, 55, 59, 10, 1|, 12, 13. and 14 and the switch means- 15, 15, 11 and 48 to the, motor 40 and the coil 41 I in a manner which may readily be understood by referring to this figure. This current will soon be sufiicient to energize the motor, but if d r d the motor may be'initially started'by operati ely-l0 connecting it to any other suitable source of elec- I trical supply. 0 j J The fan-39 drives an air stream around and between that portion of the thermopile constructions above the insulating board ||.q This air stream blowing against the cold junctions and I the straps supporting them by reason of their connection with the pipes 32, rapidly-withdraws the heat from the cold junctions thereby maintaining a substantial difference in temperature 80' between the cold and the hot junctions.

Herethe straps 25' have a very important func-,, tion. They are so connected to the cold junctions and have such a large radiating surface that the heat is quickly transferred from the cold 55',

junctions to the air. It will be observed that each of these straps are thermally and electrically in-. sulated from the pipes 22 by the asbestos sleeves 24: After the air stream has ,passed through a portion of the thermopile construction above the o the size of the air stream, and thus compels a a larger number of heat units to pass through a ,square inch taken cross sectionallyo the air stream in .the'tube than wouldpassthrough a square inch taken cross sectionaliy of the air stream in front of the funnel shaped conduit 4|. This condition tends to heat that portion of'the fins positioned within the tube 44, and this heat is conducted to'the outer portion of the fins. A

minor portion of the ai'rstream passes through 5118 090111388 43 and between the outer portions 56 'ofthefins. f

Due to the heating of the fins by the constric-v tion and'compression of the air streamas it through the conduit 4|, the temperature of the minor portion of the air stream is subto stantially-heated before-passing downwardly intothe, conduit ll and the' interior of the firebox. It will thus be seenathat alarge portion of the heat energy transmitted to the" air stream is recovered and utilized in heating the junctions of as the thermopile which lie beneath theboard, ll.

Itis, of course, desirable that any electrical generating system should be capable of maintaining a substantially constant voltage at the main terminals of the "generator. The-valve 56 and 10 switch construction e e'cts a voltage control whereby this objectmay be attained. The coil and the spring 52 are so designed and adapted t if the voltage is above thelmaximum voltage at which the system is intended to operate, the 15' magnetic pull on the armature ll against 'theten- M I nerating apparatus.

voltage is suilicient tocause enough current to flow through the coil to overcome the tension of .the spring and set the valve 56 onthe valve seat 65. This, of course, shuts oi! the fuel supply and reduces the temperature of the hot junctions of my thermopile construction. If desired the switch arm 60 maybe so arranged as to open the circuit between the switch terminals I. In this event the fan is, of course, stopped and the Theshield ll maybealsoweldedtoa rectangular ring 04 having a U-shaped groove This ring may be welded or otherwise connected to the plate 8i, and the side walls of the combustion chamber which, of course, contains a burner (not shown). which supplies the heat to this thermopfle construction. Any other suitable source of heat may be employed.

The main purpose of the casing II is obviously fuel supply is entirely cut on. and the voltage of vto permit any suitable cooling fluid medium such 10 the current generated rapidly falls below the predetermined minimum voltage of the system.

Under these conditions the magnetic pull exerted against the tension ofthe spring 62 is weak- 1 ened sufllciently to cause the valve to open and the switch lever arm 60 to short the switch terminals 8|.

A continuous extreme limit reciprocating movement of the movable elements of the valve and switch construction sufllcient to alternately close and open its switch and valve is not, of course, essential to the normal operation of my device The voltage of the generator may usually be controiledby a small increaseor decrease of the sion of the spring '2. in is readily apparent that a slight increase in 1 the magnetic pull will cause the valve to gradually reduce the amount of the fuel which passes through the .valve chamber 52, and into the burner O. The reducing of the fuel supplied to :the burner 9; of course, reduces thepotential dif- 41 and the plunger 58.

- coil 41.

. ported by a steel plate IL, Thisference impressed on the generator terminals 32 and 33 and the magnetic pull exerted by the coil It is obvious, therefore, that thevoltage generated by this system may be controlled within narrow limits, andthat these limits may be varied by regulating a rheostat l9 whichis placed in series with the windings of the In Figure 9 r'iiave shown fragmentariiy a modiadapted to be water cooled.- This generator has a rectangular asbestos composition board I I sunwhich shield the hot junctions '84 from coming in direct' contact with the heated particles of combustion in thecombustion chamber 85. These junctions are. electrically insulated from the cuplike members 82 by cup-shaped insulators I. These insulators may, if desired, be made of any suitable material such as, forinstance, asbestos or mica compounds or compositions.

The cold junctions 81 of the thermopile may, if desired, be si in constructioneto the cold junctions in the preferred format my invention, and may be similarly secured together. These junctions are, however, soldered or otherwise directly connectedjzo' metal bars 88;; These bars may beg-made of copper or copper alloy or any suitable material adapted to serve as good heat conductors. j i These bars are provided with openings ll adapted to receive supporting pipes 22"-which may. be

supported in any suitable manner. The pipes 22' are electrically insulated fromthe metalbars by meansof an insulating sleeve 2|. The metal I bars '8 are covered' by a rectangular. metal shield II which may be made of a steel alloy. This shield 10 is adapted to cover a plurality of the cold junctions and their bars, and is arrangedito be-welded i or otherwise secured in a water tight manner to a I rect ngular casing, 9|, whichis provided with a we inlet port and ,awater outlet port 93.

as, for instance, cold water or liquid sulphur di-. oxide to be passed stand the bars'll-and the cold junctions for the purpose of maintaining a large diiference in temperature between the upper and lower junctions of the modified form of my inven 16 tion.

Bythe provision of the II on the hot ends of the couples to .reduce resistance and increase heat absorption and by intimately connecting thebgckets of hangers 28 as by welding to upper en '0 oftbecoupleelementsontheop to f side of the insulating partition to provide efllcient heat radiation, a high temperature diil'erence can be obtained notwithstanding the use ofrelatively short thermocouple elements to provide a compact :5

By utilizing relatively short couple members, electrical resistance is reduced and by paralleling the absorbers and the hot junctions and likewise the radiators with the cold junctions resistance a,

-. junctions, since the couple elements cannot conduct heat to the cold junctions and the radiators tions. I

While I have shown certain modiflcations army invention for the purposof'illustration, I do not wishtoberestricted speciilcally thereto so limitedbythe appended claims.

1. In a thermoelectric generating system ofthe character described, alcombustion chamber, a burner positioned in the combustion chamber. an insulating board forming an upper portion ofthe boundary of said chamben'a plurality ofmetal thermocouple strips operatively connected together to form a thermcpile extendinithrough the board .into the combustion chamber, and having their, c cold .iunctions extending above said a plurality of metal supporting and he'at radiating, meansdirectly connected to said cold jimctions for supporting said thermocouple strips in posig5 means for supporting supporting and 11 the insulating partition tothe cold .5,

iledform of a thermoelectric generator which is. enacted by the radiators connected to the cold P e 1188 in quantities suillcient to reduce substantially the integral up-like. portions or corrugations l2 temperature menu or the wt P com jun? except as and having hot junctions projecting 'means for separating saidair stream into a major air stream and a minor air stream and for reducing the cross sectional'areaof the stream, means for passing said minor air stream around said major air and metal head raditing means secured to said slotted funnel tube to;

major airform a thermopile having its'hot junctions promeans, and projecting within and without said tunnel tube means for conducting heat from said major air stream to said minor air stream and conveyor means for passing said minor air stream into said combustion chamber.

2. In a device oi the character described a combustion chamber provided with insulating walls, an insulating board forming a part 0'! said walls,

a burner located in the combustion chamber, a-

plurality of thermocouple elements passing through said board extending on each side thereof, and being operatively connected together to jecting within the combustion chamber and its cold junctions projecting without the combustion chamber, fan and conduit means for driving an air stream around the cold junctions of the thermopile, funnel means for constricting and exhausting a major portion of said air stream and for passing a minor portion of said air stream around the major portion of said air stream, and

conduit means for guiding the minor portion of 10 

